1. Field of the Invention
The present invention relates to an infrared-sensitive color developing composition, a lithographic printing plate precursor, a plate making method for a lithographic printing plate, and a new compound that can be preferably used as an infrared-sensitive color developer.
2. Description of the Related Art
At the moment, lithographic printing plates are produced using computer to plate (CTP) technologies. That is, lithographic printing plates are produced by directly scanning, exposing, and developing lithographic printing plate precursors using lasers or laser diodes without using lith films.
In response to the above-described technological advances, regarding lithographic printing plate precursors, there is a changing demand for improvement in image-recording characteristics, printing characteristics, physical characteristics, and the like in accordance with the CTP technologies. In addition, due to increasing interest in the global environment, regarding lithographic printing plate precursors, there is another attention-gathering environmental demand for good treatments of waste liquid used for wet processes such as a development process.
Regarding the above-described environmental demand, there have been attempts to facilitate development or plate-making or to remove processes. As one of easy plate making methods, a method called “on-machine development” is carried out. That is, in the method, after the exposure of lithographic printing plate precursors, development of the related art is not carried out, and instead, the lithographic printing plate precursors are mounted on printers, and unnecessary portions in image-recording layers are removed at the initial phase of an ordinary printing step.
In on-machine development-type or process-less (development-less)-type lithographic printing plate precursors on which no development process is carried out, there are no images on the printing plates in a phase of mounting the printing plates on printers, and thus plate inspection is not possible. Particularly, whether or not it is possible to determine if register marks, which serve as indicators for registration in polychromatic printing, are drawn is critical in printing operations. Therefore, for on-machine development-type or process-less (development-less)-type lithographic printing plate precursors, there is a demand for means for checking exposed images, that is, the generation of so-called print-out images in which exposed regions develop or do not develop colors. Furthermore, from the viewpoint of improving workability, there is another demand that exposed regions which develop or do not develop colors remain unchanged regardless of the elapsing of time and maintain a state of developing or not developing colors.
In addition, as lithographic printing plate precursors of the related art, lithographic printing plate precursors described in JP2013-199089A are known.